第(10)问的极限怎么求?求解题过程 10
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lim(x->1) ( x^(1/3) -1)/(x^(1/2) -1)
=lim(x->1) ( x^(1/6) -1) ( x^(1/6) + 1)/[ (x^(1/6) -1).(x^(1/3) + x^(1/6) +1) ]
=lim(x->1) ( x^(1/6) + 1)/ (x^(1/3) + x^(1/6) +1)
= ( 1+1)/(1+1+1)
=2/3
=lim(x->1) ( x^(1/6) -1) ( x^(1/6) + 1)/[ (x^(1/6) -1).(x^(1/3) + x^(1/6) +1) ]
=lim(x->1) ( x^(1/6) + 1)/ (x^(1/3) + x^(1/6) +1)
= ( 1+1)/(1+1+1)
=2/3
追问
看不太懂
追答
x^(1/3) -1 = (x^(1/6))^2 - 1^2 =( x^(1/6) -1) ( x^(1/6) + 1)
x^(1/2) -1 = (x^(1/6))^3 -1^3 =(x^(1/6) -1).(x^(1/3) + x^(1/6) +1)
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